Bituminous paint and method of making the same



Patented June28, 1938 BITUMINOUS PAINT AND METHOD OF MAKING THE SAME Edward James Canavan, Te'aneck,;N.'"J., assignor.

to The Barrett Company, New 'York, N. Y., a "corporation of New Jersey .1 No Drawing.

This invention relates tobituminous paints, and more particularly, to bituminous paints or coating compositions for protecting metal-surfaces having oil or grease. spots, 1. e., films of oil or grease, thereon and'to procedures formaking such paints and protecting'such surfaces.

Metal pipes, andyparticularly steel pipes, which are coated in the field with coal tar pitch are usually primed at the mill-With a coal tar paint or primer. The priming coat must be continuous, i. e., free of'barespots. Otherwise; while in transit, rust spots will develop on the pipes. The barespots in the priming coat-may be largely dueto oilwor grease adhering to the pipe walls and preventing adhesion of the priming coat to the metal surface of the. pipe. In practice, it has been found expensive and practically impossible ztoiibpmpletely; remove theoil or grease mm. the

, pipe surface-atthemill where the pipe is formed and to maintain the surface entirely free from films of oil orgrease until the pipe isprimed or painted. Consequently, as heretofore practiced, the-priming of the pipe at the mill with coal tar primers has resulted frequently in poorly;primed pipes; This may be attributed to the fact that bituminous paints, and particularly tar pitch paints, such as coal tar pitch and water. gas tar pitch, when applied to steel or other metal surfaces contaminated with lubricating oil or grease, which are generally not miscible with the paint, fail to form a continuous coating over the metal surface. Hence, bare spots are left on the metal which permit subsequent corrosion of the metal when it is exposed to weathering influences. For

5 example, in the manufacture of electrically welded steel pipes for gas lines, the pipe surface'citen contains spots and streaks of lubricating oil picked up by the pipe in its passage through the forming rolls and conveying equipment of the electric welding apparatus. Such oily spots or streaks may be hardly perceptible in a casual examination but yet be sufficient to cause a faulty coating when the bituminous paint is applied.

It is an object of this invention to provide a bituminous paint, and more particularly, a tar pitch paint, which, when applied to steel or other metal surfaces bearing lubricating oil 'or grease, will form a continuous coating completely covering the metal surface and thus efficiently protect it against corrosion. Other objects and advantages will appear from the following detailed description.

I have found that even if an oil or grease film or spot be present on the metal pipe, it'can be properly primed with a bituminous paintsuch as Application February '7, 1934, Serial No.710,110, i

' 2 Claims. (01'. ni -5'1")? a tar pitch paint having incorporated therein a soapor other material having detergent properties in the presence of organic solvents. The addition: of a metallic salt of a fatty acid, e. g., a soap, to :a bituminous paint or coating composi- I tion, I have found modifies the same so that it wets and flows evenlyover lightly oiled metal surfaces, resulting inthe formation of a continuous paint film or coating on such surfaces.

.Aluminum' stearate is preferred for use in this invention because of the 1 highly satisfactory results obtained in priming oil-spotted metal-pipes,

such as steel-pipes, with the coal tar paint in whichthis material was incorporated, as hereinafter more fully described.- The addition of aluminum stearate to pitch paints, and particularly tocoal tar pitch or water gas tar pitch paints imodifies the surface tension and Wetting characteristics of the paint so that it readilycoats 'metal surfaces, including any oil or grease-bear.-

ing portions thereof, forming a continuous paint film which effectively protects the metal; Among the detergent materials which may advantageous- 1y be used in pitch paints are: other metallic salts of fatty acids such as magnesium ste'arate,,,--

zinc stearate, zinc laurate, ammonium andsub stituted ammonium soaps soluble in organic. solvents, and salts of certain sulphonic acids having detergent properties in the presence of organic solvents, e. g., sodium salts of naphthone sulphonic acids. 7

One example of a tar-pitch paint produced in accordance with my invention is given below:

A pitch base, consisting essentially of coal tar pitch, and having a melting point of from 143 F.

to 148,F. and a maximum percentage of free carbon of approximately 12 per cent, was melted. Crude solvent naphtha was then added to the melted pitch in such quantity that the resultant mixture had an Engler viscosity for 100 c. c. at 25 C. of from 175 to- 225 seconds. i

The aluminum stearate solution was prepared by adding approximately seven ounces of alumi num stearate to one gallon of crude solvent naphtha, thus forming a solution containing approximately 5 per cent by weight of aluminum stearate.

The mixture was heated slowly to a temperature of from to C., at which temperature a gel was formed. The temperatiue was 1 then slowly raised to C. and the'mixture held at that temperature for about ten minutes. During the second stage of heating, the gel-like mass changed to a syrupy solution which when cooled to about 30 C. exhibited frothing properties.

The paint was made by mixing 80 parts of the pitchzsolvent naphtha mixture with 20 parts of the aluminum stearate solvent solution. The finished paint contained approximately 1 per cent of aluminum stearate by weight; i. e., about 1.4 ounces of stearate per gallon of paint.

An important feature of this invention is the procedure following in incorporating the metallic soap in the paint. I have found that the heating of the aluminum stearate or other soap employed admixed with the solvent to a sufliciently high temperature (in the example above given, 170 C.) the gel originally formed becomes fluid and changes to a syrup which remains a syrup on cooling. The cooled syrup can readily be mixed with the other paint ingredients.

The pitch base employed in the paint may be coal tar pitch, water gas tar pitch, coal tar, water gas tar, mixtures of these pitches or tars, or other bituminous materials. The amount of pitch used in the paint may vary from 40 to 65 per cent by volume of pitch while the amount of solvent employed may vary from 35 to per cent. However, when a paint of slow drying characteristics is desired, the percentage of soft pitch maybe as high as 80 per cent, the proportion of solvent being reduced correspondingly. Whenthebase of the paint consists of tar or soft distilled tars, the percentage of solvent may be'reduced below 20 per cent, but ordinarily 10 per cent or more of solvent is necessary in a paint of suitable drying properties and hardness of paint coating.

In lieu of employing a solution of aluminum stearate or other metallic soap containing approximately 5 per cent by weight of metallic soap, as in the example above given, an aluminum stearate solution or other metallic soap solution containing up to approximately 20 per cent by weight of metallic soap may be employed. The 5 per cent solution, it was found, did not substantially alter the viscosity of the paint when added thereto. As the addition of a 20 per cent solution of aluminum stearate to the pitch: solvent mixture would alter the viscosity, a mixture of pitch and solvent of lower viscosity may be used with the 20 per cent solution than is used with a 5 per cent solution, so that the finished paint has substantially the same viscosity as the paint of the example hereinabove given. If a low viscosity paint is desired, aluminum stearate solutions containing less than 5 per cent of aluminum stearate by weight may be employed, or a mixture of pitch and solvent of lower viscosity may be combined with a solution of metallic soap containing at least 5 per cent of metallic soap. The 5 amount of aluminum stearate in the finished paint may vary from 0.5 per cent to 5 per cent by weight, 1 per cent by weight of aluminum stearate being preferred.

Instead of the solvent naphtha, drip oil, coke oven light oil, or distillates obtained from coal tar, water gas tar, or the oils mentioned may be employed to flux the coal tar pitch, water gas tarpitch, coal tar or other bituminous base employed in making the paint. Preferably, the boiling point of the solvent or flux used should be within the range of from 100 C. to 220 C. Other organic liquids may be employed as solvents for the pitch in the manufacture of the paint, as for example carbon tetrachloride.

The paint may be applied to'the metal or other surface either by spray or brush application or by dipping the metal surface into a bath of the paint.

It is to be understood that this invention is not restricted to the present disclosure otherwise than defined by the appended claims.

I claim:

1. A fluid, brushable paint consisting of from 40 to percent by volume of pitch from the 39 group consisting of coal tar pitch and water gas tar pitch, from 35 to 60 percent by volume of solvent for said base, and a small amount of aluminum stearate dissolved in said solvent whereby said aluminum stearate is permanently and 35 homogeneously distributed in dissolved form through said paint.

2. The process of making a bituminous paint containing from .5 per cent to 5 percent by weight of aluminum stearate which comprises mixing (40 said aluminum stearate with solvent naphtha, heating the resultant mixture to a temperature of from to C. until a gel is formed, continuing the heating until the gel is changed to a syrup, cooling the syrup and, mixing the same :45 with a mixture comprising pitch derived from coal and 10 to 60 per cent by volume of a solvent therefor.

EDWARD JAMES CANAVAN. 

